Considerations regarding Temperature Measurement using RTDs for Industrial Process Plants

This paper presents a review of the key factors to be considered when a temperature instrumentation system is designed for high-temperature processing plants such as nuclear power and petrochemical industry plants. In particular, three main error factors influencing the accuracy of the RTDs (Resistance Temperature Detectors) are reviewed and addressed in this paper. Among the various temperature sensors, RTDs are used the most commonly for high-temperature control and monitoring systems in industrial plants thanks to their excellent accuracy and stability compared to other sensors. Although the EMF effect may become slightly bigger, it is recommended to design an RTD instrumentation circuit with a low excitation current or voltage to reduce the self-heating effect unless the usage of a low current ruins the noise immunity feature of the circuit. In addition, because the compensation of lead wire resistance in RTD circuits is an essential factor to be addressed, it is desirable to carefully review the installation circumstances and connection configuration of a temperature sensor.